You will execute a
Problem
Isolation
Exercise to locate the corrupted element that is causing the wacky 3D file.
This problem is most likely an irrational slab or a library part.
To loacte the bad element, turn off 1/2 of the layers and see if the problem persists. If not, then you know it is in the other 1/2 of the layers.
Show 1/2 of them. If not, etc... Through this process of elimination, you can find the layer where the bad part is.
Take this element out and beat it until it behaves.
Dwight Atkinson